Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
Codeine vs APOMORPHINE HYDROCHLORIDE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Codeine is an opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception. It is a prodrug converted to morphine via CYP2D6, which mediates most of its analgesic effects.
Non-ergoline dopamine agonist with high affinity for D2 and D3 receptors, moderate affinity for D4, D5, and adrenergic receptors; activates striatal dopamine receptors to improve motor function.
FDA-approved for mild to moderate pain where an opioid is appropriate,FDA-approved for cough suppression,Off-label: acute pain, chronic pain (limited use)
FDA: Acute treatment of hypomobility episodes ('off' episodes) in Parkinson disease,Off-label: Refractory erectile dysfunction, treatment of levodopa-induced dyskinesias, depression
Oral: 30-60 mg every 4-6 hours as needed; maximum 360 mg per day. Intramuscular/Subcutaneous: 30-60 mg every 4-6 hours as needed. Use lowest effective dose for shortest duration.
Subcutaneous injection: 0.2 m L (2 mg) test dose, then 0.2-0.6 m L (2-6 mg) as needed for acute hypomobility episodes; maximum single dose 0.6 m L (6 mg). Sublingual: 2-10 mg sublingually as needed, not more than every 2 hours, maximum 30 mg/day. Continuous subcutaneous infusion: 0.5-2.0 mg/hour via infusion pump.
The terminal elimination half-life of codeine is approximately 2.5 to 3.5 hours in adults with normal renal function. In patients with renal impairment, the half-life may be prolonged to up to 8 hours, necessitating dose adjustment.
Terminal elimination half-life is 40–60 minutes in adults with normal renal function; prolonged to 3–6 hours in end-stage renal disease.
Codeine is metabolized by CYP2D6 to morphine (active), via CYP3A4 to norcodeine (inactive), and via glucuronidation. Morphine is further conjugated via UGT2B7.
Hepatic via CYP3A4, CYP2C9, and CYP2C19; main metabolite is apomorphine-8-O-sulfate; first-pass effect with rapid clearance.
Codeine is eliminated primarily via renal excretion (about 90% as inactive metabolites, mainly codeine-6-glucuronide and norcodeine, with less than 10% as free codeine). Biliary/fecal excretion accounts for approximately 10% of the dose.
Approximately 90% of an intravenous dose is excreted in urine within 24 hours, primarily as unchanged drug and sulfate conjugates. Biliary/fecal excretion is minimal (<5%).
Approximately 25% bound to plasma proteins, primarily albumin.
Approximately 90–99% bound, primarily to albumin.
Approximately 3-6 L/kg, indicating extensive distribution into tissues, including brain and breast milk.
1.8–2.5 L/kg, indicating extensive tissue distribution.
Oral bioavailability is about 60-90% (first-pass metabolism reduces systemic exposure; extensive metabolizers may have higher morphine levels). Rectal bioavailability is similar to oral. Intramuscular and subcutaneous routes have nearly 100% bioavailability.
Subcutaneous: 100% (absolute); sublingual: 16–18%; oral: <1% due to extensive first-pass metabolism.
Cr Cl 10-50 m L/min: Administer 75% of normal dose. Cr Cl <10 m L/min: Administer 50% of normal dose. Not recommended in severe renal impairment due to risk of CNS toxicity.
No dose adjustment for mild to moderate impairment. Severe impairment (GFR <15 m L/min): avoid use as apomorphine is renally eliminated and accumulation may occur; use with caution and reduce dose if necessary at GFR 15-29 m L/min.
Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 50% or use alternative. Child-Pugh Class C: Contraindicated. Avoid in severe hepatic impairment due to decreased metabolism and risk of accumulation.
Child-Pugh A and B: no dose adjustment necessary. Child-Pugh C: pharmacokinetics not studied; use with caution and monitor closely.
Oral, IM, or SC: 0.5-1 mg/kg/dose every 4-6 hours as needed; maximum 60 mg/dose. Weight-based dosing for children >1 year. Not recommended in children under 12 years for postoperative tonsillectomy/adenoidectomy. Contraindicated in children <12 years for pain, and <18 for cough due to risk of respiratory depression.
Safety and efficacy not established; no pediatric dosing recommendations.
Start at low end of dosing range (e.g., 30 mg every 4-6 hours) due to increased sensitivity and risk of respiratory depression, falls, and cognitive impairment. Monitor renal function and avoid in patients with Cr Cl <30 m L/min. Consider non-opioid alternatives first.
Elderly patients may be more sensitive to neuropsychiatric effects; initiate at low end of dosing range (e.g., 1-2 mg subcutaneously) and titrate slowly; monitor for hypotension and falls.
WARNING: CODEFINE HAS RISKS OF ADDICTION, ABUSE, AND MISUSE, WHICH CAN LEAD TO OVERDOSE AND DEATH. LIFE-THREATENING RESPIRATORY DEPRESSION MAY OCCUR, ESPECIALLY IN CHILDREN, AND RISK IS INCREASED WITH CYP2D6 ULTRA-RAPID METABOLIZERS. PROLONGED USE DURING PREGNANCY CAN RESULT IN NEONATAL OPIOID WITHDRAWAL SYNDROME.
None.
CYP2D6 ultra-rapid metabolizers: risk of morphine toxicity, fatal respiratory depression,Life-threatening respiratory depression in children <12 years; contraindicated in <18 years for tonsillectomy/adenoidectomy,Risk of opioid-induced respiratory depression, especially in elderly, debilitated, or patients with respiratory conditions,Addiction, abuse, and misuse potential,Neonatal opioid withdrawal syndrome if used during pregnancy,Concomitant use with CNS depressants increases risk of hypotension, respiratory depression, and coma,Serotonin syndrome with serotonergic drugs,Severe hypotension, including orthostatic hypotension,Adrenal insufficiency with prolonged use,Increased risk of seizures in patients with seizure disorders,May impair ability to drive or operate machinery
Risk of hypotension, syncope, and orthostatic hypotension,Severe nausea and vomiting (pretreat with antiemetic),Potential for hallucination, dyskinesia, and impulse control disorders,Do not mix with serotonin 5-HT3 antagonists (e.g., ondansetron) due to severe hypotension,Use caution in patients with cardiovascular disease, hypotension, or renal impairment
Hypersensitivity to codeine or any component,Significant respiratory depression,Acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment,Paralytic ileus (known or suspected),Postoperative management in children <18 years after tonsillectomy/adenoidectomy,Children <12 years,Use with MAOIs or within 14 days of stopping MAOIs
Concurrent use with serotonin 5-HT3 antagonists (e.g., ondansetron),Hypersensitivity to apomorphine or sulfite-containing products,Severe asthma or sulfite allergy
Avoid alcohol completely; increase risk of CNS depression and hepatotoxicity. Grapefruit juice may inhibit CYP3A4, affecting codeine metabolism; limited data but caution advised. High-fiber foods may help counteract constipation. No significant food restrictions aside from alcohol.
Avoid alcohol: may increase drowsiness and hypotension. Grapefruit juice: may increase risk of QT prolongation. No specific food interactions; maintain normal diet but monitor for changes in blood pressure.
FDA Pregnancy Category C. First trimester: association with neural tube defects, cleft palate; second/third trimester: risk of fetal dependence, respiratory depression, withdrawal after birth. Avoid in labor due to neonatal respiratory depression.
Apomorphine hydrochloride is a dopamine agonist indicated for Parkinson's disease. Limited human pregnancy data; animal studies show fetotoxicity and teratogenicity at doses near maternal toxic doses. FDA Pregnancy Category C. First trimester: Avoid use unless benefit outweighs risk. Second/third trimester: No established safety; potential fetal effects include altered dopamine receptor development. Postnatal: Risk of neonatal withdrawal if used near term.
Codeine is excreted into breast milk; M/P ratio approximately 2.0. Use with caution; risk of infant opioid toxicity, especially in CYP2D6 ultra-rapid metabolizers. Not recommended for breastfeeding mothers.
No data on apomorphine excretion in human milk. M/P ratio unknown. Due to potential for serious adverse reactions in breastfeeding infants (e.g., somnolence, hypotension, dyskinesia), breastfeeding is not recommended during therapy.
Increased clearance and volume of distribution in pregnancy may require higher doses for analgesia; however, avoid due to risks. No standard adjustment; use lowest effective dose for shortest duration if necessary.
Pregnancy can alter apomorphine pharmacokinetics due to increased plasma volume, renal blood flow, and hepatic metabolism. No specific dose adjustment guidelines exist. Use lowest effective dose with careful titration. Monitor for reduced efficacy or increased adverse effects (e.g., hypotension, nausea).
Codeine is a prodrug requiring CYP2D6 metabolism to morphine; poor metabolizers have reduced efficacy, while ultra-rapid metabolizers risk toxicity. Avoid in children <12 years for post-tonsillectomy/adenoidectomy due to fatal respiratory depression. Monitor for constipation; prescribe laxative with chronic use. Contraindicated with MAOIs and within 14 days of their discontinuation. Not effective for acute pain needing immediate relief due to variable conversion.
Administer subcutaneously; avoid intravenous use due to risk of hemolytic anemia and hypotension. Onset is rapid (5-15 minutes) with short duration (1 hour). Use an antiemetic (e.g., domperidone or trimethobenzamide) for 3 days before starting to prevent nausea. Do not use with 5-HT3 antagonists (e.g., ondansetron) due to profound hypotension. Monitor for dyskinesia, orthostatic hypotension, and QT prolongation. Avoid in patients with dementia, psychosis, or severe respiratory depression; caution in hepatic/renal impairment. Test dose (0.2-0.5 m L) is required before first prescription.
Take exactly as prescribed; do not increase dose or frequency without consulting your doctor.,Do not combine with alcohol, sedatives, or other CNS depressants (e.g., benzodiazepines) due to risk of severe drowsiness, respiratory depression, or coma.,Common side effects include constipation, nausea, dizziness, and drowsiness. Drink plenty of fluids and consider stool softeners for constipation.,Avoid driving or operating machinery until you know how codeine affects you, as it may impair judgment and coordination.,Inform your doctor if you have a history of asthma, breathing problems, liver or kidney disease, or if you are pregnant or breastfeeding.,Do not share this medication with others, especially children; accidental use can be fatal. Store securely out of reach of children.,If you miss a dose, take it as soon as you remember. If near the next dose, skip the missed one; do not double dose.,Do not stop abruptly after prolonged use; taper under medical supervision to avoid withdrawal symptoms (anxiety, sweating, insomnia, diarrhea).
Take this medication exactly as prescribed; it is for on-demand treatment of 'off' episodes.,Inject under the skin (subcutaneous) as directed; do not inject into a vein or muscle.,You may feel dizzy or lightheaded when standing up; rise slowly from sitting or lying down.,Nausea is common; your doctor may prescribe an anti-nausea medicine to take before each dose.,Report any chest pain, fainting, or severe dizziness immediately.,Avoid alcohol and grapefruit juice while using this medication.,Do not change your dose or frequency without consulting your doctor.,Keep this medication away from children and pets.
"Pirenzepine, a selective M1 muscarinic antagonist, reduces gastrointestinal motility and secretions, while codeine, an opioid agonist, also decreases gastrointestinal motility via mu-opioid receptors. Concurrent use leads to additive anticholinergic and opioid effects, resulting in enhanced risk of severe constipation, paralytic ileus, and central nervous system depression. Clinically, patients may experience exacerbated sedation, respiratory depression, and urinary retention."
"Ropinirole, a non-ergoline dopamine agonist used in Parkinson's disease and restless legs syndrome, may reduce the analgesic efficacy of codeine. This is likely due to pharmacodynamic antagonism at central dopamine and opioid receptors, as well as potential pharmacokinetic interactions that decrease the conversion of codeine to its active metabolite morphine via CYP2D6 inhibition by ropinirole. The resultant blunted opioid response can lead to inadequate pain control, necessitating dose adjustment or alternative therapy."
"Vemurafenib induces CYP3A4, significantly reducing the plasma concentrations of codeine, which is metabolized via CYP3A4 to its active metabolite morphine. This may diminish codeine's analgesic efficacy, potentially leading to inadequate pain control. Additionally, reduced formation of morphine may lower the risk of opioid-related adverse effects."
"Coadministration of morphine with palbociclib may increase plasma concentrations of palbociclib due to morphine-induced inhibition of intestinal P-glycoprotein (P-gp) efflux transporter and potential competition for CYP3A4 metabolism. This elevation can heighten the risk of palbociclib-related toxicities, including myelosuppression (neutropenia, leukopenia, anemia), hepatotoxicity, and gastrointestinal adverse effects (e.g., diarrhea, nausea). Patients should be monitored for signs of excessive palbociclib exposure and dose reductions considered if toxicity occurs."
"Morphine, a potent opioid analgesic, can inhibit the metabolism of sulfisoxazole, a sulfonamide antibiotic, by competing for hepatic glucuronidation pathways. This pharmacokinetic interaction leads to increased plasma concentrations of sulfisoxazole, potentially elevating the risk of dose-dependent adverse effects such as crystalluria, hypersensitivity reactions, and bone marrow suppression. Co-administration requires careful monitoring for sulfonamide toxicity, especially in patients with renal impairment or those receiving high-dose morphine."
"Morphine is a potent opioid analgesic that can inhibit the metabolism of isavuconazonium (prodrug of isavuconazole) via competitive inhibition of CYP3A4, the primary enzyme responsible for its activation. This leads to reduced conversion to the active antifungal isavuconazole, potentially decreasing its efficacy against invasive fungal infections. Conversely, isavuconazonium may also inhibit morphine metabolism, increasing opioid side effects such as respiratory depression, sedation, and constipation."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about Codeine vs APOMORPHINE HYDROCHLORIDE, answered by our medical review team.
Codeine is a Opioid Agonist that works by Codeine is an opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception. It is a prodrug converted to morphine via CYP2D6, which mediates most of its analgesic effects.. APOMORPHINE HYDROCHLORIDE is a Opioid Agonist that works by Non-ergoline dopamine agonist with high affinity for D2 and D3 receptors, moderate affinity for D4, D5, and adrenergic receptors; activates striatal dopamine receptors to improve motor function.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between Codeine and APOMORPHINE HYDROCHLORIDE depend on the specific clinical indication. These are both Opioid Agonist agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of Codeine is: Oral: 30-60 mg every 4-6 hours as needed; maximum 360 mg per day. Intramuscular/Subcutaneous: 30-60 mg every 4-6 hours as needed. Use lowest effective dose for shortest duration.. The standard adult dose of APOMORPHINE HYDROCHLORIDE is: Subcutaneous injection: 0.2 m L (2 mg) test dose, then 0.2-0.6 m L (2-6 mg) as needed for acute hypomobility episodes; maximum single dose 0.6 m L (6 mg). Sublingual: 2-10 mg sublingually as needed, not more than every 2 hours, maximum 30 mg/day. Continuous subcutaneous infusion: 0.5-2.0 mg/hour via infusion pump.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
A moderate-severity drug interaction has been identified when combining Codeine and APOMORPHINE HYDROCHLORIDE. The risk or severity of adverse effects can be increased when Morphine is combined with Codeine. Consult your prescriber before combining these medications.
The maternal-fetal safety profiles differ. Codeine is classified as Category D/X. FDA Pregnancy Category C. First trimester: association with neural tube defects, cleft palate; second/third trimester: risk of fetal dependence, respiratory depression, withdrawal . APOMORPHINE HYDROCHLORIDE is classified as Category D/X. Apomorphine hydrochloride is a dopamine agonist indicated for Parkinson's disease. Limited human pregnancy data; animal studies show fetotoxicity and teratogenicity at doses near m. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.